Heptane Reforming over Pt–Re/Al2O3: Reaction Network, Kinetics, and Apparent Selective Catalyst Deactivation

Abstract

This is a continuation of our previous work aimed at developing a fundamental, a priori model for predicting how a reforming catalyst deactivates in a fixed-bed reactor due to coke formation. Specifically, we construct a lumped reaction network for n-heptane reforming on a bifunctional Pt–Re/Al2O3 catalyst using both differential and integral rate data. The data are obtained from a vibrational microbalance and a multioutlet fixed-bed reactor with n-heptane or reaction intermediates as the feed. The network, including a five-membered naphthene lump that is the primary coke precursor, has a minimum number of reactions and corresponding adjustable rate parameters, almost all of which are individually determined by targeted experiments. The resulting kinetic model, coupled with a previously developed catalyst coking kinetic model, correctly predicts the long-term spatiotemporal behavior of product composition and coke-on-catalyst for a fixed-bed reformer. The results strongly suggest the need to partition the reforming reactions into two subgroups: those that are significantly affected by coke and those that are not. The approach taken here, which provides both fundamental insights and a quantitative basis for improving catalysts and processes, can also be extended to other catalytic systems.